Tunable antenna

Description (excerpt)

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. Licensing and technical inquiries may be directed to the Office of Research and Technical Applications, Naval Information Warfare Center Pacific, Code 72120, San Diego, CA, 92152; (619) 553-5118; NIWC_Pacific_T2@us.navy.mil. Reference Navy Case Number 212390. BACKGROUND Dual-band antennas send and receive signals in two separate distinct bands while a broadband antenna sends and receives signals over a wide range of frequencies. Dual and broadband antennas can typically either operate at different frequencies sequentially or simultaneously depending on the application. The advantage of dual and broadband antennas is that these antennas reduce the footprint of the antenna when compared to multiple single band antennas. As a result, dual and broadband antennas can be used in space-limited applications. One example includes cellular or dual-band wireless access points. In addition, dual and broadband devices can be inexpensive making them useful for a wide range of applications. DESCRIPTION OF THE DRAWINGS Features and advantages of examples of the present disclosure will be apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, but in some instances, not identical, components. Reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear. FIG. 1 is a perspective view of an example of a dual-band or broadband antenna without the top plane; FIG. 2 is another perspective view of an example of a dual-band or broadband antenna with the top plane and ground plane; FIG. 3 is another perspective view of an example of a dual-band or broadband antenna with a cross-element top plane with four equilateral elements; FIG. 4 is another perspective view of an example of a dual-band or broadband antenna with a cross-element top plane with eight equilateral elements; FIG. 5 is another perspective view of an example of a dual-band or broadband antenna without the top plane; FIG. 6 is a bottom 2D view of an example of the inner ground plane of the dual-band or broadband antenna; FIG. 7 is a plot of the return loss (X-axis labeled “Return Loss Dual Band Antenna 3B Half Sphere) vs. the frequency (Y-axis labeled “mag(S-parameters) (dB)”) of an example of a dual-band antenna disclosed herein; and FIG. 8 is a plot of the frequency (X-axis labeled “FieldStorageFrequency (GHz))” vs. realized gain (Y-axis labeled “RHCP Realized Gain (dBi)) of an example of a dual-band antenna disclosed herein. DETAILED DESCRIPTION A nanosatellite are satellites that are equal to or less than 10 kg in mass. A CubeSat is an example of a nanosatellite that has a size of 1.33 kg and dimensions of 10 cm×10 cm×10 cm. Nanosatellites have limited space for antennas due to their size. As a result, nanosatellites have extremely limited space for antennas in general. Currently, multiple antennas are used in nanosatellites to support the required frequency bands to transmit and receive signals. Consolidating the antennas to a single antenna that can support dual or broadband frequencies on a nanosatellite has not been accomplished. The tunable antenna herein can be incorporated onto a nanosatellite as a single antenna that supports a dual-band frequency or broadband frequency. The tunable antenna includes a broad frequency spectrum that allows the antenna to transmit and receive any necessary signal. As a result, this antenna saves space, weight, and money by reducing the number of antennas that can be used towards other functions of the satellite. The antenna herein is a tunable or dual-band antenna includes a ground plane, a top plane, a cage structure, a first half-loop, a second-half loop, and a hybrid phase shifter. The ground plane is composed of a metallic material of a satellite structure or a base of a ground station antenna. The cage structure is attached to the ground plane and a top plane. The cage structure includes four leg structures in electrically-conductive contact with the top plane. The top plane is one of a cross-element with four equilateral elements, a cross-element with eigh